(a) Field of the Invention
The present invention relates to a variable resistance measuring loop having a compensation function for environmental factors, and in particular, a measuring loop used in a mouse cursor controller which will not be affected by environmental factors, but will reduce circuit defect rates and upgrade the precision of the mouse cursor controller.
(b) Description of the Prior Art
Among computer peripherals, a computer mouse cursor controller is one of the most indispensable in operating a computer. A computer mouse, keyboard, handwritten board, and joystick are exemplary peripherals which provide the function for controlling the movement of the mouse cursor in controlling and operating the computer in documentation and image handling or in accordance with game software.
Conventionally, the mouse cursor controller hardware is used to control x-axis and y-axis movements on a display. In this controller, an RC charging/discharging circuit calculates the coordinates of movement based on the charging/discharging of a capacitor C. However, due to the influence of the environment, for instance, changes in temperature and humidity, the value of the capacitor C of the RC charging/discharging circuit may be altered. This leads to an unstable circuit, causing the controlling of a mouse or joystick not to be smooth. In a more serious case, equipment may be damaged, such that its calibration cannot be restored to the normal state.
Accordingly, it is an object of the present invention to provide a variable resistance measuring loop having a compensational function for environmental factors, wherein a loop is used in the mouse cursor controller circuit to overcome the above drawbacks.
Accordingly, it is an object of the present invention to provide a variable resistance measuring loop having a compensation function for environmental factors, wherein two ends of a variable resistance connected to a control loop which is connected to a capacitor charging/discharging device are employed. The amount of movement is calculated via a discharging equation, and due to the two ends of the variable resistance being connected accordingly, the measuring loop is not affected by environmental factors in the mouse cursor controller circuit.
Yet another object of the present invention is to provide a variable resistance measuring loop having a compensation function for environmental factors wherein a central processing unit, CPU, has a first terminal thereof connected to one end of the variable resistance and a second terminal thereof connected to the other end, a center contact of the variable resistance being connected to a collector of a charging switch transistor Q. The base of the transistor Q is connected in series with a resistance R to a third terminal of the CPU; the emitter of the transistor Q is connected to a VDD power source; and, the drain is coupled to a fourth terminal of the CPU, and connected in series with a charging/discharging capacitor C to common ground. By means of the two ends of the variable resistance being connected to a control loop which is connected to a capacitor charging/discharging device, the amount of cursor movement is calculated via a discharging formula. Additionally, the measuring loop is not affected by environmental factors bearing upon the mouse cursor controller circuit.